1. Field of the Invention
The present invention is directed to the field of internal combustion engine fuel delivery and metering systems. In particular, the present invention is directed to that portion of the above-noted field which is concerned with the delivery and metering of a liquid fuel to provide a combustible air/fuel mixture for an internal combustion engine. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the delivery and metering of a liquid fuel which has been vaporized prior to mixture with an air stream. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the vaporization of a liquid fuel in quantities sufficient to maintain the operation of an internal combustion engine in an automotive vehicle environment. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the provision of an internal combustion engine waste heat operated liquid fuel vaporizer operative to provide quantities of vaporized liquid fuel sufficient to maintain operation of the internal combustion engine. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the provision of an internal combustion engine exhaust gas system situated heat exchanger communicating with a source of liquid fuel and operative, under normal engine operating conditions, to transfer sufficient quantities of heat from the exhaust gas to the liquid fuel within the heat exchanger to provide sufficient quantities of vaporized liquid fuel to sustain engine operation. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the provision of means for modulating the temperature of an exhaust gas actuated liquid fuel vaporizer. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the provision of a liquid fuel vaporizer positionable within the exhaust gas conduit of an internal combustion engine having means responsive to the temperature of a vaporized liquid fuel to modulate the quantity of exhaust gas being supplied to the liquid fuel vaporizer.
2. Description of the Prior Art
It is well known in the prior art to provide a fuel in liquid form to a moving air stream for delivery to the combustion chambers of an internal combustion engine. The prior art systems generally have utilized mechanical or electromechanical fuel delivery and metering apparatus to provide metered quantities of liquid fuel in proximity to, and in some cases into, the combustion chambers of an internal combustion engine. The prior art has also taught that a quantity of liquid fuel may be added to a quantity of moving air upstream from, and for ultimate delivery to, a plurality of combustion chambers through a plurality of intake manifold conduits. The advent of federally mandated internal combustion engine exhaust emission standards has resulted in the investigation of techniques to substantially reduce the quantity of pollutants produced by an internal combustion engine. One technique proposed to reduce the quantity of atmospheric pollutants generated by an internal combustion engine has been to prevaporize the liquid fuel prior to delivery to the air stream. The basis of this proposal is the improved ability to control, from cylinder-to-cylinder within any one internal combustion engine, the air/fuel ratio of the combustion mixture. Experimental results have indicated that to the extent to which the air/fuel ratio may be controlled more accurately, the ability to implement techniques for the reduction of atmospheric pollutants generated by the internal combustion engine may also be increased.
The prior art contains a substantial number of suggestions directed to the vaporization of a liquid fuel for use in a fuel delivery system for an internal combustion engine. These prior art solutions have generally centered around using the exhaust gases of the internal combustion engine as a source of heat for heating a liquid fuel stream. However, the prior art suggestions have not been wholly technically feasible in terms of providing a vaporized liquid fuel to an internal combustion engine in an automotive environment. In particular, the automotive environment requires that fuel be delivered to the internal combustion engine with mass flow rates which may vary by a factor of 20:1. Any liquid fuel vaporizing system must therefore be capable of accommodating vaporization of liquid fuel which may be consumed by the engine with mass flow rates which vary by 20:1.
A further problem which has not been adequately addressed by the prior art involves the recognition that commercially available gasolines can be expected to be completely vaporized at temperatures above about 425.degree. F. The temperature of the exhaust gases produced by an internal combustion engine can readily be substantially in excess of this value. It is therefore a specific object of the present invention to provide a liquid fuel vaporization apparatus for insertion within the exhaust gas system of an internal combustion engine which apparatus includes means to vary the temperature of the vaporization apparatus. It is also an object of the present invention to provide liquid fuel vaporization apparatus which is adapted to accommodate vaporization of a liquid fuel having a mass flow rate which may vary by a factor of 20:1. In accommodating an engine which may consum masses of fuel which may vary by a substantial margin, the cross referenced copending commonly assigned patent application teaches the use of a variable volume vapor reservoir. It is therefore a further and specific object of the present invention to provide a liquid fuel vaporization apparatus for charging a vapor reservoir.